Search results

The purpose of this study is to analyse numerically and experimentally the effects of lip thickness (LT) and bypass ratio on co-flowing nozzle under subsonic and correctly expanded sonic jet decay at different Mach numbers.

Co-flowing jets from co-flowing nozzles of different LTs, 0.2, 1 and 1.5 Dp (where Dp is the primary nozzle exit diameter = 10 mm), with an annular gap of 10 mm at main jet exit Mach numbers 0.6 have been studied experimentally and the other cases have been performed numerically. The co-flowing jet with 2 mm LT was used for comparison.

Co-flowing jet axial pitot pressure decay, axial static pressure decay, axial velocity decay, radial velocity decay and streamline velocity contours were analyzed. The results illustrate that the mixing of the co-flowing jet with profound LT is prevalent to the co-flowing jet with 2 mm LT, at all Mach numbers of the current study. Also, the LT of the co-flowing jet has a strong impact on jet mixing. Co-flowing jets with 10 mm and 15 mm LT with a constant co-flow width of 10 mm experience a considerably advanced mixing than co-flowing jets with 2 mm LT and a co-flow width of 10 mm.

The application of bypassed co-flow jet is in turbofan engine operates efficiently in modern civil aircraft.

All subsonic jets are considered correctly expanded with negligible variation in axial static pressure. However, in the present study, static pressure along the centerline varies sinusoidally up to 9% and 12% above and below atmospheric pressure, respectively, for primary jet exit Mach number 1.0. The sinusoidal variation is less for primary jet exit Mach numbers 0.6 and 0.8 in static pressure decay.

THE following notes, principally for the use of ground engineers, refer to the super‐charging of the four‐stroke cycle petrol engine; two‐stroke cycle engines and compression ignition engines are not here dealt with.

An investigation has been carried out by Quo‐Tec Limited, on behalf of the Department of Trade and Industry's Advanced Sensors Technology Transfer Programme, to determine the opportunities which exist in the UK transportation industries for advanced sensors. The study was concerned particularly with the identification of new business opportunities for UK Small and Medium‐sized Enterprises (SMEs). The study's boundaries were defined as the automotive, aerospace, rail and marine transportation sectors and the advanced sensor technologies of optical fibres and solid state. Piezoelectric, capacitive, inductive magnetoresistive, thin film, thick film and micromachined silicon devices were all included in the term solid state. These were highlighted because of the proven strength of UK research in many of these areas and yet, in many cases, a current lack of significant UK commercial exploitation. Through literature reviews, extensive telephone interviews and face‐to‐face discussions with key individuals in over 90 transportation companies, sensor companies and research institutions, a similar number of sensor requirements were identified. From this number, those requirements best addressed by optical or solid state sensor technology were selected. A criterion applied in the selection was that the need could be addressed by a UK SME (either alone or in collaboration) with a reasonable expectation that a sensor could be commercially available within five years. Preferably, proven technology should be available — the job of a sensor company is to develop the technology into a commercial product, not to do the fundamental research work to prove the technology itself. This article comprises some “prime” opportunities, thus identified, applicable to the automotive industry.

This emergency generating system was first fitted on the 01 and 02 pre‐production Concordes and will be installed on the production aircraft. Initial design work commenced in 1967 and a fully developed and type‐tested unit went into production in 1971.

Purpose of the study is to further expand insights into how weather impacts attendance at sporting events. With the NFL having only eight home games a year per team, it is more of an event than other North American sports. We explore this in terms of how sensitive fans are to weather, by not only looking at traditional factors, but also other weather variables available through Accuweather. In addition, the authors explore team success, outcome uncertainty and other factors as determinants of demand.

The method includes Tobit model of attendance in terms of percent of capacity in the National Football League. Model includes factors such as outcome uncertainty, team success, etc. but mainly focuses on weather. Weather factors studied include traditional variables such as temperature and precipitation, and also includes cloud cover, barometric pressure, wind speed and humidity. Different model specifications are included to explore results. Key findings allow for differences between games played outdoors versus indoors.

In terms of control variables, team success, new stadiums and stadium age play a significant role in attendance in terms of percentage of capacity. Outcome uncertainty does not appear to be important, and fans desire the opposite when the home team is an underdog. The main results concern the weather. When only traditional weather variables are included, precipitation plays a key role. With further expansion of the weather variables, it appears that cloud cover offers some additional information beyond precipitation. In addition, barometric pressure plays a minor, but statistically significant role as it relates to attendance in terms of capacity.

Including deeper and richer weather data helps to further explain attendance at sporting events. With the NFL, this may be limited by it being such as event due to the scarcity of games in a season. In addition, the weather variables are not truly independent, although they are not as correlated as may be anticipated on the surface. Use of different types of weather variables in models of attendance may help to deepen our understanding of factors influencing consumer decisions. These factors may play larger roles in sports with wider variance in attendance during the season.

The practical implications are that other weather-related variables besides temperature and precipitation may offer insight into consumer decisions related to attendance at sporting events. Cloud cover gives insights into anticipated poor weather in addition to it directly leading to less of a sunny day to be outdoors at an event. Barometric pressure has been shown to influence headaches and joint pain and may also influence consumer decisions to venture out to sporting events.

As data becomes more widely available in general, it's possible to add additional insights into factors influencing various forms of decision-making. In this study, we show that more information on weather can shed insights into consumer decisions as it relates to attending events such as sports. These decisions likely differ based upon whether the event is held outdoors or indoors. With more entertainment choices as substitutes, it is important to identify key factors which influence consumer decisions to help better structure events in the future.

Weather variables beyond temperature and precipitation are included in a Tobit model for NFL attendance using percentage of capacity as the dependent variable. These weather variables are cloud cover, wind speed, humidity, and barometric pressure. Cloud cover and barometric pressure were found to have some significant effects on percentage of capacity. When included, precipitation itself is no longer found to be significant, but precipitation interacted with games played in domes retains statistical significance as there are key differences between games held outdoors versus indoors.

The annual and seasonal variation of meteorological parameters has been studied for twenty stations in Saudi Arabia. The contour maps showed temperature and rainfall increasing and wind speed decreasing trends with decreasing latitudes. The mean temperature varied between a minimum of 8.4°C and a maximum of 34.61°C while overall mean was 23.95°C. The Mean, minimum and maximum values of pressure were 932.12, 923.3 and 944.6mb, respectively. The corresponding relative humidity values were 42.7, 78.5 and 21.5%, respectively. The empirical models developed for the prediction of monthly mean values of individual parameters were able to estimate the values with acceptable accuracy

SUPERCHARGED aero engines are more or less a post‐war invasion into the practical side of aero‐engine design. The problem of power boosting for internal combustion engines, especially aero engines, has for several years engaged the attention of engine designers, with the result that to‐day quite a number of engines are produced with superchargers as an integral part of the standard equipment. Various types of superchargers have been tried, such as the reciprocating pump, Roots Blower, exhaust‐driven turbo compressor, and the gear‐driven centrifugal form of blower. The last‐named is the type most commonly used in this country at the present time.

The purpose of this study was to investigate the effect of the environmental pressure changes on the bond strength between zirconia ceramics and adhesive resin cement.

In total, 40 rectangular-shaped zirconium-oxide ceramic specimens were prepared. For surface modification, all zirconia specimens were sandblasted with 50 μm alumina particles. The composite resin discs were bonded to modified zirconia surfaces with resin cement. The specimens were divided into four groups; hyperbaric, hypobaric, hyperbaric + hypobaric and control group. The specimen underwent pressure cycles for 30 days. The shear bond strength test was performed by using the universal testing machine, and failures of the debonded samples were examined with scanning electron microscopy and light microscope.

No significant difference in bond strength was found between the hyperbaric, hypobaric and control groups after 30 days (p > 0.05). However, there was a significant difference in the hyperbaric + hypobaric group compared to the control group (p = 0.022). Also, the Weibull modulus was highest in control group and lowest in the hyperbaric + hypobaric group.

Barometric changes due to flying followed by diving may have an adverse effect on the retention of zirconia ceramics. Care should be taken in the selection of materials for dental treatment of people who are exposed to environmental pressure changes.

Mismanagement of supply chain operations may lead to waste of products and incur substantial monetary losses. This is particularly true for products with attributes that hasten deterioration, e.g. time, temperature, humidity and barometric pressure. Attribute-sensitive products must be carefully monitored throughout all supply chain processes to ensure acceptable quality to the end customers. This paper presents a comprehensive review of the scientific literature on attribute sensitive products and on attribute sensitive supply chains. The collected studies were reviewed using the content analysis method, focusing on the following aspects of attribute sensitive products: (1) industries; (2) product categories; (3) decisions involved; (4) processes; (5) current issues; (6) sustainability concerns; (7) research methods used; (8) objectives of decision makers; (9) solution approaches used; (10) incentives driving management and (11) future research issues. Based on the analysis of findings, gaps are identified, and future research directions are proposed.

Literature review and content analysis.

The authors discovered that, while the importance of product attributes vary from one industry to the other, overall the time attribute was critical in all of the industries considered in this literature review. Coordination, customer satisfaction, reliability and safety were key issues in attribute sensitive product supply chains (asp-SCs). Similar to the typical supply chains, asp-SCs face economic, social and environmental sustainability issues. However, the majority of the studies in our analysis emphasized importance of the social sustainability. The majority of the papers were reviewed and analyzed and adopted the modeling approach as a research method. Furthermore, it was found that asp-SCs were mostly driven with customer demands and social pressure.

Based on the literature review and content analysis, there are a number of directions for the work conducted in this study to be extended in several directions. First, the literature search could be expanded by relaxing some of the restrictions (e.g. include the conference papers and articles from on-line business journals). Second, additional scientific publishers can be considered (e.g. Emerald Insight–www.emeraldinsight.com; Inderscience–www.inderscience.com). The latter two extensions would allow a more precise assessment of published to date work on asp-SC operations. Third, our findings could be validated based on interviews with professionals and executives from companies dealing with asp-SCs. Such validation will allow identification of the differences between the state of the art and the state of practice.

Supply chains that handle attribute sensitive products (asps) must consider the complexity of products that significantly change their properties due to factors such as time, temperature, barometric pressure, humidity. Mismanagement of operations within such supply chains may lead to significant product waste, as well as substantial monetary losses.

This study presented a comprehensive literature review and content analysis of studies dealing with asps in the following industries: fashion, food, healthcare, humanitarian and pharmaceutical industries